The development of a photographic light-sensitive material normally involves (1) black-and-white development which comprises formation of silver images, (2) color development which comprises formation of color images or (3) a process which comprises black-and-white negative development, fogging, and color development to obtain reversal color images. The black-and-white development process normally comprises development, fixing, washing and/or stabilizing. The color development process normally comprises color development, desilvering, washing and/or stabilizing. In the washing process, chemicals and the like attached to the light-sensitive material are washed away. In the stabilizing process, an effect of stabilizing images, which is not given in the washing process, is provided. In order to effect such a washing process in a monobath so that images having excellent properties are constantly obtained, these chemicals need to be thoroughly washed away, requiring a large amount of washing solution. Similarly, in order to effect a stabilizing process in a monobath substantially without effecting a washing process so that images having excellent properties are constantly obtained, a large amount of stabilizing solution is needed. Such large amounts of processing solutions finally produce a large amount of waste fluid which causes an increase in the waste disposal cost and more environmental pollution.
Accordingly, in order to reduce environmental pollution and the cost of processing, including waste disposal, a method has been desired for maintaining excellent photographic properties while reducing the amount of processing solution to be used in the washing and/or stabilizing process. One of effective approaches has been a washing and/or stabilizing process in a multi-stage countercurrent process (See "Photographic Processing", November, 1979, pp. 29-32).
In this multi-stage countercurrent process, when the number of stages is increased, the amount of processing solutions to be used (replenishment rate of fresh solution) can be reduced while maintaining excellent photographic properties over a certain period of time. However, the increase in the number of stages causes an increase in the disposal and apparatus cost. Accordingly, the practical number of stages is limited. Even in such a practical multi-stage countercurrent washing and/or stabilizing process, if the continuous processing is effected over an extended period of time, excellent photographic properties cannot be maintained, causing an increase in yellow stain or the like.
In recent years, an approach has been proposed to process a washing solution and/or stabilizing solution through a reverse osmosis membrane for reuse so that the solution thus regenerated may reduce the replenishment rate of fresh solution while maintaining excellent photographic properties.
In the process described in JP-A-58-105150 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), the overflow solution from the washing tank is processed through a reverse osmosis membrane. The solution which has been purified through the reverse osmosis membrane is returned to the washing tank for reuse while the solution thus concentrated is returned to the prebath of the washing tank, i.e., blix tank. Thus, the blix agent carried by the light-sensitive material can be reused, enabling a reduction in the replenishment rate of fresh solution. Accordingly, the desilvering properties in the blix tank can be improved, inhibiting stain on the edge of the light-sensitive material.
The approach disclosed in JP-A-60-241053 is a modification of the above approach disclosed in JP-A-58-105150. In this modified approach, the solution to be processed through the reverse osmosis membrane is merely changed from the washing solution to a stabilizing solution. It is asserted in the reference that this approach allows a reduction in yellow stain both after a prolonged storage and shortly after processing.
However, the reverse osmosis membranes disclosed in these patents need a large area and a high pressure such as 40 to 55 kg/cm.sup.2. Accordingly, these reverse osmosis membranes are disadvantageous in that they require an expensive pressure pump to operate, thereby increasing the apparatus cost and making it difficult to put them into practical use except in some large-scale laboratories. These reverse osmosis membranes are also disadvantageous in that such high pressure causes a rise in the temperature of the solution which has permeated therethrough, deteriorating the photographic properties to be processed.
In order to eliminate these defects caused by a high pressure, JP-A-62-254151 proposes a processing method in which the overflow solution from the washing tank or the stabilizing tank is received by a reservoir, and the solution collected in the reservoir is recirculated through a reverse osmosis membrane at a pressure lower than the ordinary value so that the solution is concentrated. In this method, the pressure at which the solution is subjected to reverse osmosis can be reduced to a relatively low value such as 14 to 20 kg/cm.sup.2.
However, such an approach is disadvantageous in that if a low pressure reverse osmosis is continuously effected over an extended period of time, it causes a drop in the permeable amount of solution and clogging in the reverse osmosis membrane, which rarely take place in a high pressure reverse osmosis.
Few if any approaches for inhibiting clogging in the reverse osmosis membrane have been known except the approach described in JP-A-62-254151 which comprises the use of a chelating agent. In this approach, a chelating agent is used to inhibit clogging in the reverse osmosis membrane from the calcium or magnesium originally present in the washing solution or eluted from the light-sensitive material.
However, this approach resides in the regeneration of the washing solution and/or stabilizing solution through a reverse osmosis membrane at a relatively moderate pressure. It is found disadvantageous in that if it is applied to low pressure reverse osmosis, it initially gives less of a drop in the permeable amount of solution and less clogging in the reverse osmosis membrane but causes a drop in the permeable amount of solution and clogging in the reverse osmosis membrane after a prolonged continuous operation.
All the above-mentioned high pressure, middle pressure and low pressure reverse osmosis processes involve a drop in the permeable amount of solution and clogging in the reverse osmosis membrane, more or less. For example, some reverse osmosis processes do not cause these problems after couple of weeks of continuous operation but cause noticeable problems after a continuous operation for an extended period of times such as one month. There has been a desire to find a basic solution to these problems.
These reverse osmosis processes also cause troubles in the photographic properties of images thus obtained, particularly yellow stain shortly after processing and after storage. These high pressure, middle pressure and low pressure reverse osmosis membrane processes cause some deterioration in the photographic properties of images thus obtained after a prolonged continuous operation more or less. Thus, it has been desired to provide a process which constantly enables the formation of images having excellent photographic properties even after a prolonged continuous operation.